SIGNIFICANT ICE STORM TO IMPACT THE MID-ATLANTIC REGION SUNDAY INTO MONDAY. IF YOU HAVE NOT REPLENISHED YOUR ROAD/DRIVEWAY SALT, IT MAY BE TOO LATE AS LOCAL HOME DEPOT SUPPLIES RAN OUT QUICKLY LAST TIME.

FOR EMAIL SUBSCRIBERS: Sorry that you are receiving multiple updates of the same post, explanation for this is below. Just delete the oldest version and read only the most current.

(1) WHAT IS THE MOST LIKELY OUTCOME?

The Winter Storm Watch posted for most of Pennsylvania, Maryland, northern Virginia, West Virginia and a slice of Northern New Jersey has been upgraded to a Winter Storm Warning. The key factors coming into focus are "evaporative cooling" an increasing amount of moisture as indicated on radar, and the stubborn nature of the East Coast High Pressure ridge. As moisture falls through dry air, it evaporates, which is a cooling process. This concern has been spelled out in discussions from the DC-Baltimore NWS this morning. The net result is a reinforcement of the cold air in place, allowing what is called "Cold Air Damming" to remain and strengthen. You can see their concern just by looking at the placement of that 1032 mb High to the north and 1024 mb High in the southeast. There are also tornado watches and warnings in Alabama and Mississippi, indicating that the moisture flow is likely to continue into this storm for some time. Once it reaches the Mid-Atlantic, the double dome High pressure will have chilled considerably overnight. Warm moist air advecting over this very large area of cold air will produce extensive frozen precipitation. I know this is stronger language that I have been conveying in the previous 48 hours, but if the freezing rain scenario plays out more this time than the sleet did last time, this storm could inflict greater damage to the DC-Baltimore-Philly Metro areas than the Valentine's Day Storm.

In general this may end up an I-95 special, which means the closer you are to the interstate and it's major cities, the greater variety of precipitation you will see. In the metro areas (DC-Baltimore-Philly) I can envision this event starting as light snow Sunday morning, then transitioning to snow/sleet in the late morning, then sleet/freezing rain by noon. There could be a brief period of plain rain Sunday afternoon along and east of 95 before reversing course back to freezing rain and sleet, ending as snow showers. Areas north and west of that line will see less mixed precip, but are still likely to experience more snow/sleet and less freezing rain or rain. One key difference that stands out between this storm and that of 2/14 is the much larger area of ice shown on current radars. That storm had a snow shield extending from Philadelphia to Nebraska at one point, and had a thin band of ice until it reached the Mid-Atlantic. Look back through the archives to last week and see the differences. That alone should indicate we are in for a very disruptive event.

In central and northern Maryland snow accumulations will be light, less than 2" overall south and east of MD I-81 but the ice potential will be significant and hazardous. The Balto-DC NWS in their Winter Storm Warning text go as far as saying "travel will be difficult to impossible." If you follow storms like I do, I can tell you that's the first time the NWS in this area has used that phrase. What happened in Anne Arundel and Prince Georges counties last time might be the outcome in this region, with widespread power outages affecting thousands of people. With the pre-storm hype this time virtually non-existent, people may be less prepared because it seemed to come out of nowhere for those not closely monitoring it like we do.

In northern Virginia/eastern West Virginia and northwestern suburbs of DC, a freezing rain advisory is in place and this could very well end up a repeat of last week, with the same areas and experiencing power outages and the same school systems closed for more than one day. Lower southern Maryland, which has a Winter Weather Advisory, southeast Virginia and the Del-Mar-Va will see brief periods of mixed precip, starting as snow/sleet before quickly changing over to rain by noon, ending as rain and snow showers Monday.

In central/east central Pennsylvania and New Jersey, snow will primarily be the issue, and areas between I-76 to I-80 will see at least 3 inches mixed with sleet. Freezing rain and sleet will mix in at times south of I-76 holding down accumulations of snow for those areas. I may have to revise these projections based on how storm dynamics unfold over the next 12 hours. Southeastern PA and the Philadelphia region are more likely to have an evenly distributed but "mixed bag" meaning those areas will see a plowable amount of snow (3-4 inches) as well as sleet and freezing rain but all occuring at different times.

(2) HOW WILL THIS IMPACT MONDAY?

Since a Winter Storm Warning has been issued and significant accretion of freezing rain and sleet is expected to up to 1/4 inch by late Sunday night, it is not unreasonable to expect many schools and universities will be delayed or closed Monday morning. The commute will no doubt be hazardous if the current expectations verify. As for speculation on schools being closed...it is going to come down to the depth and extent of icing, and whether or not temperatures rise to the point that it is clear to district officials that enough warming would take place Monday morning to warrant a delay. This would occur if the scientific data suggests that sun angle and surface temperatures being right at 32 would be enough that roads will improve by the time buses are rolling for first round of pickups at 8:30 AM. In Pennsylvania schools will run the whole gamut of possibilities..some closed, others open and forced into an early dismissal. Don't try to make sense of how that's going to unfold. In the case of Maryland's large county systems such as Baltimore, Frederick, Carroll, Harford, Howard, etc... I believe it will be an example of the "2/3rds - 1/3rds" rule. If two-thirds of a particular county are under undeniably icy conditions, while the other one-third has changed to rain, then that school system is likely to close. If the reverse is true, I would expect a delay.

(3) HOW DEFINITE IS THE UNCERTAINTY ?

Very. We are perhaps 18 hours out from onset of precip in the metro areas, and computer models continue to show inconsistencies, with respect to arrival time, precip type and amounts. I am certain this will be a uniquely different storm from the Valentine's Day event, and could very well be worse from an icing standpoint. From this point forward, our storm becomes a "NowCast" event meaning that as the situation unfolds, computer models may not pick up on all the nuances and changes you see by radar, satellite and surface observations. Real-time upper air analyses (especially 850 millibar levels) become critically important in determining depth of cold air, wind vectors and extent of moisture available as indicated by vertical soundings and dewpoints. This data will be among the key factors in figuring out what these storms are going to do over the next 48 hours. The other interesting factor I have not seen discussed as much in Baltimore NWS headlines is how much the secondary storm impacts the region, whereas this is mentioned more in the PHL warning statements.

Other questions you have which I will address later:

(4) WHERE DID THIS STORM COME FROM ?

(5) WILL THERE BE ANY MORE AFTER THIS ONE ?

Regarding the email update feature, I have discovered that when a new post is published, the service generally sends you the update immediately. The disadvantage is however that when I return to the post for editing or revisions, the Feedblitz service views that revision as new information, and sends you a second version. This results in your emailbox receiving two or three messages which look like I'm violating my rule of not bombarding you with constant updates. If you are receiving this message as one of three notices, just delete the two earliest ones and the most recent is the final version.

I wish I could just put it all in one update, but Saturdays are a busy time at the Foot weekend childcare center, so that in combination with a complex storm forecast means the update is issued in pieces as child crises or lack thereof permit. For example, in the time it took you to read the first two sentences of this paragraph, earlier this morning the 14 month old, (who is fond of exploring in the trash can,) discovered the paper coffee filter filled with..yes..grounds. And where did the coffee grounds go you might ask? Anywhere they could possibly go as allowed by the Laws of Physics. The trash can is now sitting way up high on a table. As for the complex storm forecast, well it's already arrived at my house in the form of a highly energetic pre-toddler who is about to wake up from her nap.

For our frequent readers, we should activate the "evening news roundup" and if you can please post later tonight in the comments our usual spread of reports on what the evening news weather forecasters are conveying to the public. I will not have time to catch the news tonight and an interested to hear their prognostications.

28 comments:

Whether or not you are in a public or private school system...if you post a comment here, please consider the following:

1. Your supervisor (or mine) may be reading this, and doing so fairly regularly during a winter weather event.

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These people are:Department Chairs, Assistant Principals, School Principals, Directors, School Superintendents, CEO's and business leaders, government employees at the local, state and federal level, military personnel, university professors, network meteorologists, members of the medical profession at Johns Hopkins among other regional hospitals..to name a few.

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Thank you all for your continued support and readership. Our next storm looks to be very interesting, so off to the races we go!

I left on Valentine's Day and as we were sitting on the runway our pilot said that the airport was closed due to freezing rain. We waited an hour in the plane and took off for a "short break" in the weather.

First stop was Venice, right in the middle of Carnival. (Italian Mardi Gras) It was amazing with all the people dressed up in their ornate costumes. It was in the 50's there.

Then we went to Florence. Weather there was amazing with highs around 60.

Then was Sorento and we went to Pisa and Pompey. The palm trees were amazing down south in Italy with oranges and lemons the size of little soccer balls. Down south temperatures were around 65-70. It rained in Pisa and Pompey but once that sun came out...wow!

We finished in Rome. The first day was a little rainy, but the last day (THU) was amazing at the Vatican..temperatures were around 70 with unlimited sun. St. Peter's was amazing and I got some holy water from there.

Now that that is all said and done, time for the weather! Storm threat Sun-Mon looks to be interesting. I'm so behind so I hope to post soon.

If you are a true analytical-type person who really enjoys a challenge and have a lot of free time today... take a look at Penn State's "E-Wall" computer model website. http://www.meteo.psu.edu/~gadomski/ewall.html

A little background..In the early 90's I was one of many "Student Meteorologist" with the Penn State Weather Center (or the Campus Weather Service) at the 6th floor ivory tower of the Walker Building. It was great fun albeit extremely extremely intense work.I would get up at 3:45 AM, get to Walker by 4:30 and work with my crew to start preparing forecasts for 10 or so radio stations across Central Pennsylvania, the entire PSU campus, and recording the forecast on the PSU telephone network. While I was not a full blown shift manager, there were a number of times I filled in and did the WHOLE SHEBANG myself until the rest of the crew arrived. Gosh it makes me tired just thinking of it now. Those days I had to start no later than 3:30 AM to be ready by 5ish.

Anyway, this was back in the facsimile era (which is still used today in the big govt agencies/universities/NHC) when all the computer models were printed out on hugely long rolls of giant facsimile paper. It took an hour just to get all the maps unfurled, separated, placed in proper position by time on a long wall of model projections. Then you set about the task of analyzing all the data, satellite, surface obs, what the previous forecast shift said, comparing the models, and so on. There was not time to socialize and carry on, because around 5:40 AM, the first radio station would call expecting you to be ready to record a "today, tonight, tomorrow" forecast as well as a brief discussion.

It was a relief when you had your shift crew there..very hardworking kids they were. We were all 20-21-22 years old but were focused on this stuff like hair on a gorilla because thousands of people from all over PA were going to be hearing us talk the weather on their morning radio programs. Mind you this was way way before we even had a hint of email or anything like it. All the 4casts were prepared by hand, read over the phone, and all the analysis was done by staring at "the wall" for a long, long time.

With the advent of the high speed computer era, Mr. Fred Gadomski, a highly accomplished and esteemed meteorology professor whom advises the Campus Weather Service.. spearheaded the creation of e-Wall. And now all that incredible data we would manage.. you can now access on your computer from the comfort of home.

So I have a unique perspective and appreciation for what meteorologists do because I used to play one once. And whenever a complex storm is looming, I often think back to what it was like at

the wall.

Some other time I'll tell you the story of when I put my finger in the wrong place at the wrong time when working with the big fax machine. My Dad remembers that one like it was yesterday.

Welcome welcome back Dr. EH. (yes you were promoted to PhD in the interim). So glad you returned safe and there was snow to greet you. I-95 and friends have not seen a Kahuna yet but we're due for another KaSLOPa this weekend as you already know.

There are rumblings of one final event next weekend.. maybe you can go peering through the crystal ball of computer models and see what you find for us.

Mr. Foot,It is weird, this storm seems to be more intense with the outcome that is exspected than the last one. It is weird, there has not been that much talk about it as the last storm. This has me worried! Would you say I'm crazy?

A) Never, EVER use a halide salt on unsealed concrete (that's a salt with Cl. Br, I, F). It absolutely trashes the concrete and causes "spalling", or surface scaling.

B) Moot point, as Home Depot said that all of the salt is gone until next season...at least the oone that I stopped at in Parkville. I do a lab involving road salt and melting snow...and I wanted to do a Part II on Monday will mag chloride. (none in school) No luck!

1. The chat will be disabled from 10PM to 6AM, it needs to rest overnight for the big storm.

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Bottom line: You misbehave, you are blocked. Permanently.

It's not even dinner time yet and I blocked two users already.

This is about the weather and related issues, not a sounding board for personal agendas.

This storm looks great; I always love the anticipation before the storm. At the moment Accu-weather is predicting an inch or less of snow and 1/4-1/2 inch of ice. Accu-Weather is also saying that it is going to start earlier than most other web sites, as early as AM 5:00. Mr. Foot, I was planning to go to Round Top tomorrow leaving home at about AM 8 and leaving Round Top around PM 4 do you think that the roads will be getting bad by then?

Thank you for all the time you devote to giving us an awesome forecast!

Terp.. I have "traction melt CI" it's NaCl, KCl and MgCl2. says it is environmentally safe. No BR, pure Cl or K in the formula. However says not to use on pre-cast concrete steps,which I have. These steps were poured in the mid 80's and they've stood the test of time so far. What do you think, is the salt I have what it says to be?

Crazed SBer.. if you leave at 8AM it will take you 2-3 hours to get there and 2-3 to get back. You know that back road to Roundtop is going to be a wreck. Better to leave now, stay overnight up there somewhere.

Tarentz..glad to see other Penn Staters are here. Yeah a winter time 8AM class at Walker from East Halls would be like crossing the Arctic Tundra!

The grocery store was crazy. Might think that it's the end of days! Does anybody know where winter weather expert Paul Kocin is these days? Welcome back EH, sounds like you had a wonderful trip, and you still get to come back to winter weather, now that is special!!

Wow this could be a real mess. It is currently 31 here and we are under a winter storm warning. We actually have the message about hazardous or impossible driving conditions. They are calling for up to an inch of snow /sleet before it changes over to freezing rain. Calling for 1/4 to 1/2 inch of freezing rain tomorrow with an additional 1/4 of ice/freezing rain tomorrow night. Actally the calm before the storm in the media(lack of hype) makes me feel like this could be a huge mess. I also worry that a lot of people may be highly affected due to a lack of planning. I for one just sent my hubby to get baby formula, just in case.

If you have been using that salt without any ill effects, my opinionis that you've been fortunate.Once the salt hits water, it ionizes, and you HAVE pure chlorine and potassium (actually, chloride, so the company isn't lying.Eventually, the ions will allow the water the become "wetter" (this is not a scientific explanation!), seep deeper into the concrete, and when it freezes (no danger with this storm...too warm), it will expand and cause spalling.

Morning everyone. So glad this is not Monday the suspense would be killing me.

35 F in Dundalk, no precip. Thought AccuWx too aggressive with start time at 5AM, I felt 7-8 more likely. Suspicions about cloud cover holding up temp proved true. 40F at Inner Harbor when low was supposed to be in low 30's. Wonder if this will impact 4cast for today? Off to radar and satellite.